Over dilation

ABSTRACT

A device, system and method for dilating a patient during a minimally invasive surgical procedure is disclosed. A surgical dilation system includes a dilator having an outer tubular member and an inner tubular member sized to be movably received within an inside diameter of the outer tubular member. The outer tubular member includes a vertical slot running through a side of the outer tubular member. The inner tubular member has an upper portion and a lower portion. The retractor has a proximal end including at least one mounting member protruding outwardly from a side surface of the retractor and a distal end including at least one fanned blade protruding outwardly from the side surface. When the inner tubular member is oriented in a first position the vertical slot is in a closed state, when the inner tubular member is oriented in a second position the mounting member is permitted to travel downwardly a predetermined distance in the vertical slot, and when the inner tubular member is positioned in a third state the mounting member is permitted to freely travel through the vertical slot.

BACKGROUND

The present invention relates generally to percutaneous surgeries andmore particularly, to devices, methods and systems for performingpercutaneous, minimally invasive spinal surgeries.

Traditional surgical procedures for pathologies located deep within thebody can cause significant trauma to the intervening tissues. These openprocedures often require a long incision, extensive muscle stripping,prolonged retraction of tissues, denervation and devascularization oftissue. Most of these surgeries require a recovery room time of severalhours and several weeks of post-operative recovery time due to the useof general anesthesia and the destruction of tissue during the surgicalprocedure. In some cases, these invasive procedures lead to permanentscarring and pain that can be more severe than the pain leading to thesurgical intervention.

Minimally invasive alternatives such as arthroscopic techniques reducepain, post-operative recovery time and the destruction of healthytissue. Orthopedic surgical patients have particularly benefited fromminimally invasive surgical techniques. The site of pathology isaccessed through portals rather than through a significant incision thuspreserving the integrity of the intervening tissues. In some instances,these minimally invasive techniques require only local anesthesia. Theavoidance of general anesthesia reduces post-operative recovery time andthe risk of complications.

Minimally invasive surgical techniques are particularly desirable forspinal and neurosurgical applications because of the need for access tolocations deep within the body and the danger of damage to vitalintervening tissues. For example, a common open procedure for discherniation, laminectomy followed by discectomy requires stripping ordissection of the major muscles of the back to expose the spine. In aposterior approach, tissue including spinal nerves and blood vesselsaround the dural sac, ligaments and muscle must be retracted to clear achannel from the skin to the disc. These procedures normally take atleast one-two hours to perform under general anesthesia and requirepost-operative recovery periods of at least several weeks. In additionto the long recovery time, the destruction of tissue is a majordisadvantage of open spinal procedures. This aspect of open proceduresis even more invasive when the discectomy is accompanied by fusion ofthe adjacent vertebrae. Many patients are reluctant to seek surgery as asolution to pain caused by herniated discs and other spinal conditionsbecause of the severe pain sometimes associated with the muscledissection.

In order to reduce the post-operative recovery time and pain associatedwith spinal and other procedures, micro-surgical techniques have beendeveloped. The objective of any minimally invasive procedure is toaccomplish the same clinical objectives as the traditional, open surgerywhile minimizing soft tissue retraction. Existing sequential dilationprocesses consist of inserting multiple increasing diameter dilatorsuntil the correct diameter is achieved. A tubular retractor is thenplaced over the dilators and the dilators are then removed. Theretractor is left in place with the surrounding muscle and tissue havingbeen dilated out of the working space.

For some applications, it is beneficial to have an alternate blade shapeon the distal tip of the retractor to assist in holding back muscle andtissue during the procedure. As such, a need exists for a device thatwill allow alternate blade shapes to be used during the dilationprocess.

SUMMARY

According to one aspect a surgical dilator is disclosed that isconfigured to dilate an incision and tissue in a patient. The surgicaldilator includes an outer tubular member having a vertical slot runningalong a vertical axis from a distal end of the outer tubular member to aproximal end of the tubular member. An inner tubular member is sized andconfigured to be received within an interior of the outer tubularmember. The inner tubular member includes an upper portion having agenerally semi-circular cross-sectional shape along a horizontal axistransitioning to a lower portion having a tubular shape with a slottherein. The inner tubular member is operable to be movably positionedin a first position in which the upper portion and the lower portionclose the vertical slot in the outer tubular member, a second positionin which the lower portion closes the vertical slot, and a thirdposition in which the vertical slot is exposed.

In one form, the outer tubular member includes a head portion having avertical groove transitioning downwardly from an upper surface of thehead portion to a predetermined depth in the head portion. The headportion includes an internal circumferential groove connected with thevertical groove. The inner tubular member includes a protrusionextending outwardly from the upper portion of the inner tubular memberthat is sized to fit within the vertical and circumferential grooves.The outer tubular member includes a first head portion upon which alower surface of a second head portion of the inner tubular member restswhen the inner tubular member is positioned within the outer tubularmember. In yet another form, the inner tubular member includes aprotrusion that is positioned within a guide track that is formed in thefirst head portion.

According to another aspect, a surgical dilator is disclosed that isconfigured to dilate an incision and tissue in a patient. As with theprevious aspect, the surgical dilator includes an outer tubular memberincluding a slot running along a vertical axis of the outer tubularmember and a head portion having a larger outside diameter than aninsertion portion of the outer tubular member. The head portion of theouter tubular member includes a guide track. An inner tubular member issized to be received within the outer tubular member. The inner tubularmember has a protrusion that is sized to be received within the guidetrack such that movement of the inner tubular member is restricted bythe guide track. In another form, an inner surface of the outer tubularmember is configured with a protrusion that is configured to be receivedwithin a guide track located on an outer surface of the inner tubularmember.

The inner tubular member has an upper portion having a generallysemi-circular cross-sectional shape along a horizontal axis and a lowerportion having a slot. The inner tubular member is configured to berotated within the guide track such that in a first position the innertubular member completely closes off access to the vertical slot, asecond position in which the upper portion of the inner tubular memberexposes the vertical slot, and a third position in which the verticalslot is entirely exposed.

In one form, the inner tubular member includes a second head portion ata proximal end of the inner tubular member that is configured to rest onan upper surface of the head portion of the outer tubular member whenthe protrusion is positioned within the guide track. A lower end of theouter and inner tubular members can include an inwardly tapered tip. Theguide track is defined by a vertically oriented groove connected with acircumferential groove formed in an interior wall of the head portion.

According to yet another aspect, a surgical dilation system is disclosedthat is configured to dilate an incision and tissue in a patient andthen retract the incision and tissue. The surgical dilation systemincludes a dilator having an outer tubular member and an inner tubularmember sized to be movably received within an inside diameter of theouter tubular member. The outer tubular member includes a vertical slotrunning through a side of the outer tubular member. The inner tubularmember has an upper portion and a lower portion. The retractor has aproximal end including at least one mounting member protruding outwardlyfrom a side surface of the retractor and a distal end including at leastone fanned blade protruding outwardly from the side surface. When theinner tubular member is oriented in a first position the vertical slotis in a closed state, when the inner tubular member is oriented in asecond position the mounting member is permitted to travel downwardly apredetermined distance in the vertical slot, and when the inner tubularmember is positioned in a third state the mounting member is permittedto freely travel through the vertical slot.

In one form, the upper portion of the inner tubular member has agenerally semi-circular cross-sectional shape along a horizontal axis.The lower portion of the inner tubular member has a second vertical slotrunning therethrough having a size at least as wide the vertical slot inthe outer tubular member. The outer tubular member has a head portionhaving a guide track formed therein. The upper portion of the innertubular member includes a protrusion sized to be received in the guidetrack. The inner tubular member includes a second head portion having alower surface that rests on an upper surface of the head portion of theouter tubular member. In one form, the lower portion of the innertubular member includes a first tapered end and a lower portion of theouter tubular member includes a second tapered end that facilitatesinsertion of the dilator into the patient.

Related features, aspects, embodiments, objects and advantages of thepresent invention will be apparent from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a dilation device that comprises a plurality ofinterconnected dilators each having a larger outside diameter than theother inserted into an incision of a patient.

FIG. 2 illustrates another view of the dilation device illustrated inFIG. 1.

FIG. 3 is a perspective view of an outer tubular member of arepresentative dilator.

FIG. 4 is a perspective view of an inner tubular member of arepresentative dilator.

FIG. 5 illustrates a perspective view of the inner tubular memberpositioned within the outer tubular member.

FIG. 6 illustrates another perspective view of the inner tubular memberpositioned within the outer tubular member.

FIG. 7 illustrates another perspective view of the inner tubular memberpositioned within the outer tubular member.

FIG. 8 illustrates another perspective view of the inner tubular memberpositioned within the outer tubular member.

FIG. 9 illustrates a representative retractor having fanned blades.

FIG. 10 illustrates a surgical dilation system.

FIG. 11 illustrates another view of the surgical dilation systemillustrated in FIG. 10.

FIG. 12 illustrates another view of the surgical dilation systemillustrated in FIG. 10.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended. Any such alterations and furthermodifications in the illustrated devices, and such further applicationsof the principles of the invention as illustrated herein arecontemplated as would normally occur to one skilled in the art to whichthe invention relates.

Referring collectively to FIGS. 1 and 2, a system, device and method foruse in connection with a lumbar discectomy in which an affected nerveroot is to be decompressed will be generally discussed. Although alumbar discectomy is described herein, it should be readily appreciatedthat the principles of the present invention can be applied to manyother types of percutaneous, minimally invasive surgical procedures aswell. As such, the fact that a lumbar discectomy is described inconnection herewith should not be construed in any way as a limitationof the present invention unless expressly set forth in the claims.

A discectomy procedure typically begins with a surgeon preciselylocating the herniated disc with a very small needle that is insertedthrough the muscles of the back down to an area of the spine 10 wherespinal disc fragments 12 are located. The correct position of the needleis typically confirmed using a fluoroscope, although the use of anyimaging technology is contemplated herein. Once this is accomplished,the needle is removed and a small incision 14 is made at the puncturesite. Typically, the incision 14 length will match the outside diameterof the largest tubular dilator (e.g. −21 millimeters), which will bediscussed in detail below. A guide wire (not shown) may then be insertedinto the incision 14 and placed in the proper position in relation tothe disc fragments 12 that are to be removed. Again, a fluoroscope maybe used to confirm that the guide wire is placed in the proper position.

Once the guide wire is placed in the proper position, a first cannulatedsoft tissue dilator 16 is inserted over the guide wire and through theincision 14 to a desired depth. At this point, the guide wire can beremoved from within the first cannulated soft tissue dilator 16. Thefirst cannulated soft tissue dilator 16 may then be used to palpate theincision in both the sagittal and coronal planes. In one form, the firstdilator 16 may have an outside diameter of 12 millimeters, for example.Next, second, third, and fourth cannulated soft tissue dilators 18, 20,22 are sequentially placed over one another and inserted through theincision 14 to the desired depth. In the illustrated form, a distal end24 of each cannulated soft tissue dilator has a tapered portion to helpfacilitate insertion through the incision 14 and related muscle andtissue. Further, in other forms, one or more of the cannulated softtissue dilators disclosed herein may include depth indicators ormarkings 26 on an outside surface to help inform the surgeon as to whatdepth the cannulated soft tissue dilators have been inserted into thepatient.

In one illustrative form, the second cannulated soft tissue dilator 18has an outside diameter of 14 millimeters, the third cannulated softtissue dilator 20 has an outside diameter of 18 millimeters, and thefourth cannulated soft tissue dilator 22 has an outside diameter of 20millimeters. Although four cannulated soft tissue dilators 16, 18, 20,22 are utilized in the illustrated form, it should be appreciated thatany number of cannulated soft tissue dilators could be used in otherforms of the present invention. Further, the outside diameters of thecannulated soft tissue dilators could also vary in size in other formsof the present invention and the illustrative diameters set forth aboveshould not be construed as a limitation of the present invention. Thecannula or hollow interior portions of each cannulated soft tissuedilator is sized to fit or slide over the outside diameter of otherrespective dilators. In still other forms of the present invention,dilator 50, as discussed further below, is inserted into the patientwithout the use of sequential dilation.

Referring collectively to FIGS. 3 and 4, one representative aspectdiscloses a dilator 50 that includes an outer tubular member 52 and aninner tubular member 54. As described in greater detail below, the innertubular member 54 is sized and configured to be slidably received withinthe inside diameter of the outer tubular member 52. The outer tubularmember 52 includes a body 53 that has a circular cross-section shapethat includes a vertical slot 56 running from a proximal end 58 to adistal end 60 of the body 53. The proximal end 58 of the body 53 definesa head portion 62 that has a larger outside diameter than an insertionportion 64 of the body 53. As illustrated, the head portion 62transitions to the insertion portion 64 with the insertion portion 64having a longer length than the head portion 62. The distal end 60 ofthe body 53 includes an inwardly tapered portion 66 to help facilitateinsertion through the incision 14.

The head portion 62 of the outer tubular member 52 also includes agenerally vertical inwardly facing groove or passage 68 and acircumferential groove or passage 70. The vertical groove 68 transitionsinto and/or is connected with the circumferential groove 70 therebyproviding interconnected grooves. In one form, the groove 68 runssubstantially vertical along a vertical axis, but in other forms thegroove 68 could be diagonal or angled down toward the circumferentialgroove 70. In one form, the circumferential groove 70 runs almost, butnot entirely, around the circumference of the inside diameter of theouter tubular member 52. The circumferential groove 70 stops just beforereaching each side of the slot 56. In another form, the circumferentialgroove 70 is configured to stop the inner tubular member 54 in open andclosed states. The vertical and circumferential grooves 68, 70 form aguide track in the head portion 62 of the outer tubular member 52.

As set forth above, the inner tubular member 54 is sized and configuredto be slidably received within the inside diameter of the outer tubularmember 52. The inner tubular member 54 has a generally semi-circularcross-sectional shaped upper portion 72 along a horizontal axis and atubular shaped lower portion 74 that includes a slot 76. The tubularslot 76 is sized to have the same width as the slot 56 in the outertubular member 52. A proximal end 78 of the semi-circularcross-sectional shaped upper portion 72 includes a generallysemi-circular cross-sectional shaped tubular head portion 80. Thetubular head portion 80 has a larger outside diameter than the upperportion 72 and protrudes outwardly therefrom a predetermined distance.The upper portion 72 includes a protrusion 82 extending outwardly froman outside surface 84 of the upper portion 72. As set forth below, theprotrusion 82 is sized and configured to be received in the vertical andcircumferential internal grooves 68, 70 of the outer tubular member 52.A distal end 86 of the tubular shaped lower portion 74 includes atapered portion 88 to facilitate insertion of the dilator 50 through theincision 14. It should also be appreciated that the vertical andcircumferential grooves 68, 70 could be located on the inner tubularmember 54 facing the outer tubular member 52 and that the protrusion 82could be located on the outer tubular member 52 facing the inner tubularmember 54. In other words, the orientation of the vertical andcircumferential grooves 68, 70 and the protrusion 82 are reversed inthis form. In one form, the outer diameter of head portion 80encompasses the outer diameter of head portion 62 so that the headportion 80 of the inner tubular member 54 can rotate about the uppersurface of the head portion 62 of the outer tubular member 52.

Referring to FIG. 5, to assemble the dilator 50 the inner tubular member54 is dropped or positioned inside the outer tubular member 52 such thatthe protrusion 82 of the inner tubular member 54 fits in or is receivedwithin the vertical groove 58 of the outer tubular member 52. Theprotrusion 82 is positioned or located on the upper portion 72 of theinner tubular member 54 a predetermined distance below a lower ordistally facing surface 90 of the head portion 80. As illustrated inFIG. 6, the lower surface 90 of the head portion 80 of the inner tubularmember 54 is configured to movably rest on an upper or proximally facingsurface 92 of the head portion 62 of the outer tubular member 52 whenthe inner tubular member 54 is positioned within the outer tubularmember 52.

Once fully positioned in the vertical groove 68 of the outer tubularmember 52, the inner tubular member 54 can freely rotate horizontallywithin the circumferential groove 70 of the outer tubular member 52. Theprotrusion 82 comes into alignment with the circumferential groove 70thereby allowing rotation of the inner tubular member 54 about the outertubular member 52. In one form, the circumferential groove 70 does notreach either side of the vertical slot 56 in the outer tubular member52. The protrusion 82 of the inner tubular member 54 prevents the innertubular member 54 from travelling around the entire circumference of theouter tubular member 52. Thus, the protrusion 82 freely travels in theguide track formed by the grooves 68, 70. When the inner tubular member54 is first inserted into the outer tubular member 52, in one form, thetubular shaped lower portion 74 of the inner tubular member 54 partiallycovers the vertical slot 56 of the outer tubular member 52.

Referring to FIG. 7, at this point the inner tubular member 54 iscircumferentially rotated about the outer tubular member 52 such thatthe inner tubular member 54 is positioned in a fully closed state inrelation to the slot 56 of the outer tubular member 52. In particular,an outer side surface 94 of the inner tubular member 54, formed by theupper portion 72 and a portion of the lower portion 74 of the innertubular member 54, fully close off the vertical slot 56 in the outertubular member 54. The dilator 50 is now ready to be inserted into thepatient, such as over the fourth dilator 24 referred to in FIGS. 1 and 2in procedures in which sequential dilation is employed. In suchprocedures, the dilator 50 is inserted over the outside diameter of thelast inserted one of dilators 16, 18, 20, 22. Now, the last inserted oneof the initial dilators 16, 18, 20, 22, and any of the other previouslyinserted dilators not already removed, can be removed from the incision14 leaving dilator 50 in position in the incision 14.

Referring to FIG. 8, the inner tubular member 54 of dilator 50 is nowrotated to a half open position. In particular, inner tubular member 54is rotated such that the upper portion 72 of the inner tubular member 54no longer blocks an upper portion of vertical slot 56 of the outertubular member 52. However, a portion of the lower portion 74 of theinner tubular member 54 still closes off or blocks a lower portion ofthe vertical slot 56.

Referring to FIG. 9, a retractor 100 is illustrated that is sized andconfigured to fit within an internal passage 102 (see FIG. 8) formed ordefined by the outer and inner tubular members 52, 54. In one form, theretractor 100 has a non-circular cross-sectional shape along ahorizontal axis but it should be appreciated that retractors having acircular, generally circular, or generally rectangular cross-sectionalshape along the horizontal axis can be utilized in other aspects of thepresent invention. In particular, any cross-sectional shaped retractor100 can be utilized as long as it is sized to movably fit within theinternal passage 102 defined by the outer and inner tubular members 52,54. The retractor 100 includes a first half 104 and an opposing secondhalf 106 that each have a generally arcuate shape. The first and secondhalves 102, 104 each include one or more outwardly protruding fannedblades 108 extending from a distally end 110 of the retractor 100. Aproximal end 112 of the first and second halves 102, 104 include acylindrical post 114 extending outwardly from the proximal end 112 ofthe first and second halves 102, 104. As set forth in greater detailbelow, the retractor 100 is configured to retract the incision 14 suchthat a surgical window is formed that provides access to the surgicalarea of interest.

Referring to FIG. 10, the retractor 100 is inserted into the internalpassage 102 defined by the outer and inner tubular members 52, 54. Asillustrated, the retractor 100 is sized and configured to fit within theinternal passage 102. In particular, the retractor 100 is inserted suchthat the posts 114, and thus retractor 100, travel up and down thevertical slot 56 in the outer tubular member 52. After the retractor 100travels a predetermined distance down the vertical slot 56, the posts114 of the retractor 100 come into engagement with an upper orproximally facing surface 116 of the lower portion 74 of the innertubular member 74. As illustrated in FIGS. 11 and 12, at this point theinner tubular member 54 is rotated to a completely open position therebycompletely exposing the vertical slot 56 in the outer tubular member 52.The dilator 50 can then be pulled from the incision 14 leaving theretractor 100 in a proper orientation in the incision 14. As set forthabove, the retractor 100 can have various different cross-sectionalshapes along the horizontal axis of the retractor 100 and the dilator 50of the present invention can accommodate the extensions, posts or othersuch features (such as post elements 114) of the retractor 100regardless of the cross-sectional shape of the retractor 100.

Although various embodiments have been described as having particularfeatures and/or combinations of components, other embodiments arepossible having a combination of any features and/or components from anyof embodiments as discussed above. As used in this specification, thesingular forms “a,” “an” and “the” include plural referents unless thecontext clearly dictates otherwise. Thus, for example, the term “amember” is intended to mean a single member or a combination of members,“a material” is intended to mean one or more materials, or a combinationthereof. Furthermore, the terms “proximal” and “distal” refer to thedirection closer to and away from, respectively, an operator (e.g.,surgeon, physician, nurse, technician, etc.) who would insert themedical implant and/or instruments into the patient. For example, theportion of a medical instrument first inserted inside the patient's bodywould be the distal portion, while the opposite portion of the medicaldevice (e.g., the portion of the medical device closest to the operator)would be the proximal portion.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatall changes and modifications that come within the spirit of theinvention are desired to be protected.

1. A surgical dilator, comprising: an outer tubular member having avertical slot running along a vertical axis from a distal end of saidouter tubular member to a proximal end of said tubular member; and aninner tubular member sized and configured to be received within aninterior of said outer tubular member, wherein said inner tubular memberincludes an upper portion having a generally semi-circularcross-sectional shape along a horizontal axis transitioning to a lowerportion having a tubular shape with a slot therein, wherein said innertubular member is operable to be movably positioned in a first positionin which said upper portion and said lower portion close said verticalslot in said outer tubular member, a second position in which said lowerportion closes said vertical slot, and a third position in which saidvertical slot is exposed.
 2. The surgical dilator of claim 1, whereinsaid outer tubular member includes a head portion having a verticalgroove transitioning downwardly from an upper surface of said headportion to a predetermined depth in said head portion.
 3. The surgicaldilator of claim 2, wherein said head portion includes an internalcircumferential groove connected with said vertical groove.
 4. Thesurgical dilator of claim 3, wherein said inner tubular member includesa protrusion extending outwardly from said upper portion of said innertubular member that is sized to fit within said vertical andcircumferential grooves.
 5. The surgical dilator of claim 1, whereinsaid outer tubular member includes a first head portion upon which alower surface of a second head portion of the inner tubular member restswhen said inner tubular member is positioned within said outer tubularmember.
 6. The surgical dilator of claim 5, wherein said inner tubularmember includes a protrusion that is positioned within a guide trackformed in said first head portion.
 7. A surgical dilator, comprising: anouter tubular member including a slot running along a vertical axis ofthe outer tubular member and a head portion having a larger outsidediameter than an insertion portion of the outer tubular member, saidhead portion having a guide track; and an inner tubular member sized tobe received within said outer tubular member, said inner tubular memberhaving a protrusion sized to be received within said guide track suchthat movement of said inner tubular member is restricted by said guidetrack.
 8. The surgical dilator of claim 7, wherein said inner tubularmember has an upper portion having a generally semi-circularcross-sectional shape along a horizontal axis and a lower portion havinga slot.
 9. The surgical dilator of claim 8, wherein said inner tubularmember is configured to be rotated within said guide track such that ina first position said inner tubular member completely closes off accessto said vertical slot, a second position in which said upper portion ofsaid inner tubular member exposes said vertical slot, and a thirdposition in which said vertical slot is entirely exposed.
 10. Thesurgical dilator of claim 7, wherein said inner tubular member includesa second head portion at a proximal end of said inner tubular memberthat is configured to rest on an upper surface of said head portion ofsaid outer tubular member when said protrusion is positioned within saidguide track.
 11. The surgical dilator of claim 7, wherein a lower end ofsaid outer and inner tubular members include an inwardly tapered tip.12. The surgical dilator of claim 7, wherein said guide track is definedby a vertically oriented groove connected with a circumferential grooveformed in an interior wall of said head portion.
 13. A surgical dilationsystem, comprising: a dilator having an outer tubular member and aninner tubular member sized to be movably received within an insidediameter of said outer tubular member, said outer tubular memberincluding a vertical slot running through a side of said outer tubularmember, said inner tubular member having an upper portion and a lowerportion; and a retractor having a proximal end including at least onemounting member protruding outwardly from a side surface of saidretractor and a distal end including at least one fanned bladeprotruding outwardly from said side surface, wherein when said innertubular member is oriented in a first position said vertical slot is ina closed state prohibiting said mounting member from allowing saidretractor to be completely introduced within said dilator, when saidinner tubular member is oriented in a second position said mountingmember is permitted to travel downwardly a predetermined distance insaid vertical slot, and when said inner tubular member is positioned ina third state said mounting member is permitted to freely travel throughsaid vertical slot such that said dilator can be removed from a patientthereby leaving said retractor inserted into said patient.
 14. Thesurgical dilation system of claim 13, wherein said upper portion of saidinner tubular member has a generally semi-circular cross-sectional shapealong a horizontal axis.
 15. The surgical dilation system of claim 13,wherein said lower portion of said inner tubular member has a secondvertical slot running therethrough having a size at least as wide saidvertical slot in said outer tubular member.
 16. The surgical dilationsystem of claim 13, wherein said outer tubular member has a head portionhaving a guide track formed therein.
 17. The surgical dilation system ofclaim 16, wherein said upper portion of said inner tubular memberincludes a protrusion sized to be received in said guide track.
 18. Thesurgical dilation system of claim 16, wherein said inner tubular memberincludes a second head portion having a lower surface that rests on anupper surface of said head portion of said outer tubular member.
 19. Thesurgical dilation system of claim 13, wherein an upper portion of saidouter tubular member includes a head portion having a guide track formedtherein for guiding movement of said inner tubular member, said innertubular member including a outwardly extending protrusion sized to bereceived within said guide track.
 20. The surgical dilation system ofclaim 13, wherein an upper portion of said outer tubular member includesa head portion having a protrusion extending internally therefrom andsaid inner tubular member has a guide track sized and configured toreceive said protrusion.